1. Field of Invention
This invention relates generally to gluten-based food products and to techniques and apparatus for making these products, and more particularly to a wheat gluten food product fortified by L-lysine and seasoned to render the product exceptionally palatable.
2. Status of Prior Art
Because of the ever increasing consumption of fabricated and so-called "junk" foods that are notoriously deficient in nutritional value, there has been a concomitant growth in the demand for vegetable proteins having desirable nutritional properties. Wheat gluten, the protein fraction in wheat flour, possesses a high protein content as well as unique structural and adhesive properties. In its freshly extracted wet state it is known as gum gluten, and when thereafter dried it becomes a free-flowing powder of high protein content and bland taste. It is generally used in food processing in that form.
Wheat gluten is now widely used to fortify breakfast cereals and it is also valuable to bakers, for it acts to strengthen dough, to retain gas and to control expansion, these characteristics resulting in uniformly-shaped baked products. And because gluten absorbs about twice its weight in water, its capacity for holding water gives rise to an increased yield and extended shelf life in many food systems. The useful properties of gluten and its many advantages are set forth in greater detail in the booklet "Wheat Gluten--A Natural Protein for the Future--Today" published in 1981 by the International Wheat Gluten Association--Shawnee, Kans.
The basic procedure for manufacturing a gluten powder involves mixing flour with a dough-producing solution to produce a paste which is developed to form dough, the dough then being washed to remove as much of the starch and other soluble components as possible.
Various techniques are known to separate gluten from starch. Perhaps the oldest is the "Martin process" in which the dough, after hydration, is rolled between fluted rolls and kneaded in a trough with reciprocating rolls under water at high pressure. This action washes away the starch and leaves a mass of gluten.
In the "batter process" developed by the U.S. Department of Agriculture, a soft coherent mass of dough is mechanically broken up in the presence of additional water to yield suspended curds of gluten with the starch removed. The curds are recovered on a gyrating screen through which the starch milk passes. The "Fesca" on direct centrifugation process results in a well dispersed slurry of flour with gluten development. The starch can be removed from suspension by centrifugation while the protein remains suspended.
The more recent "Alfa-Laval" gluten extraction process is regarded in an article appearing in the publication "Milling and Baking News" of July 4, 1978 as offering advantages over earlier extraction techniques. This process converts whole wheat into a coarse flour which is mixed with water to form a thick batter. The batter is then homogenized in a disc type unit which discharges a slurry of starch, protein and other flour components. This step is followed by centrifugation which fractionates the flour into prime starch, B-starch, vital gluten and dried solubles. The 1984 patent to Guibert, U.S. Pat. No. 4,473,299, discloses a system for producing gluten continuously at a rapid rate.
It is important that the distinctions between protein extracted from grain and that incorporated in animal meat be clearly understood.
Proteins are generally classified as complete, partially complete and totally incomplete, depending on their ability to maintain life and promote growth. A complete protein contains the essential amino acids in sufficient quantities for maintenance and normal rate of growth. These proteins have a high biologic value. Animal proteins such as meat, milk and eggs are all complete proteins, though not necessarily identical in protein quality or biologic value. However, the complete proteins in animal-based foods often carry an excess baggage of fats, particularly saturated fats which are high sources of cholesterol. Moreover, they are lacking in dietary fiber.
Partially complete proteins will maintain life, but they lack sufficient amounts of some of the amino acids necessary for growth. Gliadine, found in wheat gluten, falls in this class. Adults can maintain satisfactory nutrition for indefinite periods when consuming sufficient amounts of protein from certain cereals and legumes. Totally incomplete proteins are incapable of replacing or building new tissue and, therefore, cannot support life or promote growth. The protein found in gelatin is an example of totally incomplete protein.
Certain plant foods and grains are limited in their animo acid L-lysine content (alpha, epsilon--diaminocaproic acid). When grain protein sources are supplemented by the amino acid in which they are deficient, or the food is eaten with a small amount of an animal protein source, a complete protein is then provided.
Amino acids are nitrogen-containing building blocks of proteins. The quality of a protein depends on the kinds and amounts of amino acids present in the foods in relation to body needs. Amino acids may be classified as essential and nonessential. All amino acids are necessary for the synthesis of the protein molecule. However, the body cannot produce certain amino acids; these must be supplied by food. The human adult requires eight essential amino acids; and growing children require nine or ten.
The essential amino acids include: isoleucine, leucine, L-lysine, methionine, phenylalanine, threonine, tryptophan and valine. Histidine is also essential for children. Arginine is classified as semi-essential since growth is retarded if it is not available. The presence of cystine and tyrosine in the diet will reduce the requirement for methionine and phenylalanine, respectively, and are, therefore, also semi-essential. Semi-essential amino acids include: arginine, cystine and tyrosine; nonessential amino acids include alanine, aspartic acid, glutamic acid, glycine, hydroxyproline, norleucine, proline and serine.
The properties of a protein molecule are a reflection of the combined properties of its amino acids, for these string together to form a protein's primary structure.
Vegetable and grain sources of protein lack one or more of the essential amino acids and are therefore incomplete. However, when eaten together with a complete protein complement, as for example, milk with cereal, or cheese or meat in a pasta dish, the protein in the grain is utilized as a complete protein. Complementary incomplete proteins such as rice and beans or wheat and soy also function as complete proteins. The addition of L-lysine to the wheat protein completes its amino acid profile, in a total equal to such sources as poultry, red meat or eggs. Without the addition of other foods, wheat protein also helps provide better dietary balance, in a low-fat, high-fiber composition.
Gluten as a food source is of interest in developing nations as a low-cost protein alternative to meat. In the United States, gluten-based food products follow the government's Dietary Guidelines to reduce fat and cholesterol and increase fiber and complex carbohydrates in the diet. Products currently on the market include soy, or wheat gluten meat analogs sold in health food stores. But these are not generally fortified as complete protein sources, for they lack L-lysine. Nor are they flavored for taste appeal.
In terms of American food needs, national health policies recommend changing American diet patterns to reduce fats, especially saturated fats largely derived from animal protein sources, and to increase fiber. Fiber is absent in animal proteins but well represented in wheat.
Of prior art interest are the U.S. patents to Feller, U.S. Pat. No. 3,463,770 and Damico, U.S. Pat. No. 3,878,305, and the Japanese patent 0028234.